Invoking a class from one project in another project?

I am very new to eclipse and android developing in general and need help with the following. I have built two android projects in Eclipse with the android SDK:

1. "ORF401 Project" - targets Android 2.2 platform
2. "Map Project" - targets Google APIs 2.2 platform

I have followed the steps as specified by the standard Hello World Google Maps for android tutorial and have gotten the Google map to display on the emulator when I run the second project.

I have a menu set up in the 1st project for which one of the options is to load the map. However, I'm not sure how to load the map within this project since only one build ta开发者_JS百科rget can be specified for each project, and so I cannot specify the Google Maps API as a (additional) build target. Is there a way to call the main .java class from the second project within the first project? I see where a reference can be made to the 2nd project under the project properties, but I'm not sure how to make use of this. One possible solution I found on the web was to add the following code under the switch case in the first project:

Intent intent = new Intent(this, {googleMap}.class);  
startActivity(intent);

I presume this would require an additional googleMap.java class in the first project and also another activity, but I can't get it to work. Can anyone make a suggestion as to how I can accomplish this?

If the code for either or both projects would help, I'll be happy to post it. Thanks

The main idea with projects is to have one project per application that does some thing. I assume your application needs to do something with maps, as well as something else. There is no need to split those ideas. Keep them in one project, because they make up one single application that you develop.

First thing I would suggest - read carefully about activities and intents. Head to http://developer.android.com - everything's clearly explained. With that all cleared up you will see the point in making some button, which, being tapped, opens a new screen with the map feature that you've developed. And then let's you go back or do something else, like open a new screen, a browser, etc.

And give up trying to call the other project from a different one :) It's not the way I think you want to do stuff.

Just to make sure I'm not misunderstood - of course you might want to have two projects. But those will most probably result in two separate applications. Luckily, applications may also interact by intents, or content providers, or a couple more. Just see how Contacts app takes you to GMail app if you want to send a mail. If that's what you want to achieve - still need to read about intents.

edit:
Here's the link I mentioned about in the comments:
http://android-developers.blogspot.com/2010/07/how-to-have-your-cupcake-and-eat-it-too.html
It explains how to achieve the 'additional target' that you would like to have.

There are ways to call a class from one project in another project, but there are bigger problems here. The first project can run on any Android device. The second, however, requires Google Maps APIs. You won't be able to invoke it anyway, because it can't be installed unless you're in an environment that supports Google APIs. There really is no benefit to doing this, unless you have additional functionality in project 1 such that it can exist without project 2.

I would suggest using the Intent method rather than trying to hack something together that allows you to access another class. Regardless, though coupling these two together like this seems overly complicated and error prone. I would suggest simply embedding the mapping functionality in project 1 and requiring Google APIs. Most mainstream device support them anyway.

If you're married to the idea of having two separate projects with different build targets, I would suggest looking into using BroadcastReceivers with a custom intent that you broadcast from application 1. I don't believe startActivity will work across application boundaries because of class loader issues, but I could be wrong about that.